U.S. patent number 5,783,330 [Application Number 08/715,840] was granted by the patent office on 1998-07-21 for electrode material and secondary battery.
This patent grant is currently assigned to Yazaki Corporation. Invention is credited to Hiroshi Iizuka, Katsuhiko Naoi, Yasuhiro Suzuki, Akihiko Torikoshi.
United States Patent |
5,783,330 |
Naoi , et al. |
July 21, 1998 |
**Please see images for:
( Certificate of Correction ) ** |
Electrode material and secondary battery
Abstract
An electrode material includes a sulfide compound containing an
oxadiazole ring as an active substance. The secondary battery using
such a material provides a large current at room temperature.
Inventors: |
Naoi; Katsuhiko (Tokyo,
JP), Iizuka; Hiroshi (Shizuoka, JP),
Suzuki; Yasuhiro (Shizuoka, JP), Torikoshi;
Akihiko (Shizuoka, JP) |
Assignee: |
Yazaki Corporation (Tokyo,
JP)
|
Family
ID: |
26519406 |
Appl.
No.: |
08/715,840 |
Filed: |
September 26, 1996 |
Foreign Application Priority Data
|
|
|
|
|
Sep 28, 1995 [JP] |
|
|
7-251404 |
Aug 12, 1996 [JP] |
|
|
8-212738 |
|
Current U.S.
Class: |
429/212;
429/213 |
Current CPC
Class: |
H01M
4/60 (20130101); H01M 6/181 (20130101); H01M
6/16 (20130101) |
Current International
Class: |
H01M
4/36 (20060101); H01M 4/60 (20060101); H01M
6/16 (20060101); H01M 6/18 (20060101); H01M
004/02 () |
Field of
Search: |
;429/212,213 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
CA accession number 78:91010, Haist et al. "photographic emulsions
containing heterocyclic disulfides" Jan. 21, 1972. .
Liu, Meilin et al., "Electrochemical Properties of Organic
Disulfide/Thiolate Redox Couples", J. Electrochem. Soc.,
136(9):2570-2575 (1989) month not available..
|
Primary Examiner: Nuzzolillo; M.
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
Claims
What is claimed is:
1. An electrode comprising: an electrode material including a
sulfide compound having an oxadiazole ring as an active
substance.
2. An electrode according to claim 1, wherein said sulfide compound
contains at least one member selected from a group according to
Chemical Formula (1): ##STR10## where R represents a hydrogen atom
or an organic group; and an ion according to Chemical Formula (2):
##STR11## where R represents a hydrogen atom or an organic
group.
3. An electrode material comprising a sulfide compound having a
methyl oxadiazole ring as an active substance.
4. An electrode material comprising a sulfide compound having an
oxadiazole ring as an active substance, wherein said sulfide
compound is one selected from the group consisting of 2,
2'-dithiobis (5-methyl-1, 3, 4-oxadiazole), 2, 2'-trithiobis
(5-methyl-1, 3, 4-oxadiazole), and 2, 2'-tetrathiobis (5-methyl-1,
3, 4-oxadiazole).
5. An electrode material according to claim 3, wherein said sulfide
compound is one selected from the group consisting of 2,
2'-dithiobis (5-methyl-1, 3, 4-oxadiazole), 2, 2'-trithiobis
(5-methyl-1, 3, 4-oxadiazole, and 2, 2'-tetrathiobis (5-methyl-1,
3, 4-oxadiazole).
6. An electrode material comprising a sulfide compound having a
phenyl oxadiazole ring as an active substance.
7. An electrode material comprising a sulfide compound having an
oxadiazole ring as an active substance, wherein said sulfide
compound is one selected from the group consisting of 2,
2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole), 2, 2'-trithiobis
(5-phenyl-1, 3, 4-oxadiazole), and 2, 2'-tetrathiobis (5-phenyl-1,
3, 4-oxadiazole).
8. An electrode material according to claim 6, wherein said sulfide
compound is one selected from the group consisting of 2,
2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole), 2, 2'-trithiobis
(5-phenyl-1, 3, 4-oxadiazole) and 2, 2'-tetrathiobis (5-phenyl-1,
3, 4-oxadiazole).
9. A secondary battery comprising:
a cathode made of a sulfide material having an oxadiazole ring as
an active material; and
an anode located proximate the cathode, wherein the anode and
cathode are arranged so as to form a secondary battery.
10. A secondary battery according to claim 9, wherein said sulfide
compound contains at least one member selected from a group
according to Chemical Formula (1): ##STR12## where R represents a
hydrogen atom or an organic group; and an ion according to Chemical
Formula (2): ##STR13## where R represents a hydrogen atom or an
organic group.
11. A secondary battery according to claim 9, wherein said tetrazol
ring is a methyl oxadiazole ring.
12. A secondary battery according to claim 9, wherein said sulfide
compound is one selected from the group consisting of 2,
2'-dithiobis (5-methyl-1, 3, 4-oxadiazole), 2, 2'-trithiobis
(5-methyl-1, 3, 4-oxadiazole) and 2, 2'-tetrathiobis (5-methyl-1,
3, 4-oxadiazole).
13. A secondary battery according to claim 11, wherein said sulfide
compound is one selected from the group consisting of 2,
2'-dithiobis (5-methyl-1, 3, 4-oxadiazole), 2, 2'-trithiobis
(5-methyl-1, 3, 4-oxadiazole) and 2, 2'-tetrathiobis (5-methyl-1,
3, 4-oxadiazole).
14. A secondary battery according to claim 9, wherein said
oxadiazole ring is a phenyl oxadiazole ring.
15. A secondary battery according to claim 9, wherein said sulfide
compound is one selected from the group consisting of 2,
2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole), 2, 2'-trithiobis
(5-phenyl-1, 3, 4-oxadiazole).
16. A secondary battery according to claim 14, wherein said sulfide
compound is one selected from the group consisting of the group
consisting of 2, 2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole), 2,
2'-trithiobis (5-phenyl-1, 3, 4-oxadiazole).
17. A secondary battery according to claim 9, wherein said
secondary battery is a coin shaped.
18. A secondary battery according to claim 10, wherein said
secondary battery is a coin shaped.
19. A secondary battery according to claim 11, wherein said
secondary battery is a coin shaped.
20. A secondary battery according to claim 12, wherein said
secondary battery is a coin shaped.
21. A secondary battery according to claim 13, wherein said
secondary battery is a coin shaped.
22. A secondary battery according to claim 14, wherein said
secondary battery is a coin shaped.
23. A secondary battery according to claim 15, wherein said
secondary battery is a coin shaped.
24. A secondary battery according to claim 16, wherein said
secondary battery is a coin shaped.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrode material for a
secondary battery and more particularly to a sulfide series
electrode material.
2. Description of the Prior Art
In recent years, demands for portability of communication
appliances and OA (Office Automation) appliances have intensified
competition for light weight materials and miniaturization.
Correspondingly, a secondary battery which is used as in such an
appliance or as a power source for an electric vehicle requires
high efficiency. Under these circumstances, various kinds of
batteries using new electrode materials have been developed. Among
them, an electrode material using a sulfide compound (hereinafter
referred to as a "disulfide electrode material") has been
noticeable because of its relatively high energy density as
disclosed in U.S. Pat. No. 4,833,048, the disclosure of which is
incorporated herein by reference. For example, a sulfide compound
having a triazine ring or a thiadiazole ring has been used as an
electrode material.
Assuming that the disulfide compound is represented by R--S--S--R
(R denotes an organic functional group), the disulfide bond (S--S
coupling) is cleaved by supplying two electrons by electrolytic
reduction. It is combined with a cation or proton (M.sup.+) in an
electrolytic solution to provide a salt represented by
2(R--S.sup.-.M.sup.+). The salt is returned to original R--S--S--R
by electrolytic oxidation to discharge two electrons. The secondary
battery is expected to have an energy density of 50 Wh/kg or more
which is approximately equal to that of other ordinary secondary
batteries.
However, as reported by the inventors of the above U.S. patent in
J. Electrochem. Soc, Vol. 136, No. 9, pages 2570-2575 (1989), the
electron moving speed in an electrode reaction of the
sulfide-series secondary battery is very low so that it is
difficult to take out a large current during practical use at room
temperatures. The above sulfide-series secondary battery is limited
to use at 60.degree. C. or higher.
As a technique for improving the sulfide-series secondary battery
so as to deal with a large current, as disclosed in JP-A-5-74459,
an electrode material has been propsed in which an organic compound
having a thiadiazole ring and a disulfide group is combined with a
conductive polymer such as polyaniline.
However, such an improvement did not permit a sufficiently large
current at room temperature.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a sulfide-series
electrode material which can take out a large current at room
temperature.
Another object of the present invention is to provide a secondary
battery which can take out a large current at room temperature.
In order to attain the above objects, there is provided a
sulfide-series electrode material having oxadiazole ring.
The secondary battery using the electrode material according to the
present invention can take out a larger current at room temperature
than a conventional battery using a thiadiazole ring.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cyclic voltamogram of Battery No. 1 according to an
embodiment (Embodiment 1) of the present invention;
FIG. 2 is a cyclic voltamogram of Battery No. 2 according to a
comparative example (Comparative Example 1);
FIG. 3 is a graph showing the .sup.1 H-NMR spectrum of an active
material .alpha.;
FIG. 4 is a graph showing the .sup.13 C-NMR spectrum of the active
material .alpha.;
FIG. 5 is a graph showing the .sup.1 H-NMR spectrum of an active
material .delta.;
FIG. 6 is a graph showing the .sup.13 C-NMR spectrum of the active
material .delta.;
FIG. 7 is a sectional view showing a coin-type secondary battery
fabricated in the embodiments; and
FIG. 8 is a graph showing the discharging curve (current density:
0.2 mA/cm.sup.2) in cells using active materials .alpha., .delta.
and .eta..
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the present invention, a sulfide-series electrode material
having an oxadiazole ring means a compound in which a sulfur atom
is directly combined with the oxadiazole ring and a material
containing such a compound.
Such a sulfide-series electrode material having an oxadiazole ring,
which contains an oxygen of an aromatic hetero ring, promotes
reactions of creation/dissociation of a disulfide bond.
Some of the sulfide-series electrode materials having such an
oxadiazole preferably have a group represented by chemical formula
(1) or anion represented by chemical formula (2) because of extreme
promotion of the creation/dissociation of the disulfide bond
influenced by a phenyl group. Particularly, a dimer such as 2,
2'-dithiobis (5-phenyl, 3, 4-oxadiazole), represented by chemical
formula (3) is preferable since it gives very small reduction in
the capacity even if the number of cycles is increased. A
polysulfide compound such as trisulfide having n ranging from 1 to
5 in chemical formula (3) is preferable as it can have higher
energy density.
Chemical Formula (1) ##STR1## where R represents a hydrogen atom or
an organic group.
Chemical Formula (2) ##STR2## where R represents a hydrogen atom or
an organic group.
Chemical Formula (3) ##STR3## where R represents a hydrogen atom or
an organic group, and n represents an integer of 0 to 5.
However, in the group represented by chemical formula (1) and the
ion represented by chemical formula (2), although R may be an alkyl
group such as a methyl group, an ethyl group, etc., an annular
organic material such as an amino group, a carboxyl group, an alkyl
amino group, or an amide group, an aromatic compound; or an
oxygen-introducing compound, it is preferably a group capable of
supplying electrons, such as a methyl group.
Since the above active material is not conductive, it is mixed with
an electronic conductive material and an ionic conductive material
to fabricate a positive electrode (hereinafter referred to as a
"cathode"). The electronic conductive material may be metallic
powder of carbon, titanium, nickel, etc. The ionic conductive
material may be a liquid electrolyte in which electrolytic acid
(such as perchorolate) is mixed with a solvent (such as propylene
carbonate), or a solid electrolyte (such as polyethylene oxide) in
which electrolyte acid is solved.
Both a liquid electrolyte and a solid polymer electrolyte can be
used as an electrolyte of the battery. On the other hand, the
material of a negative elecrode (hereinafter referred to as an
"anode") may be an alkaline metal or a material with the alkaline
metal removed or inserted.
EMBODIMENT 1
Evaluation by Cyclic Voltammetry Using 2, 2'-Dithiobis (5-Phenyl-1,
3, 4-Oxadiazole)
1. Synthesis of 2, 2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole)
5 mmol of iodine is dissolved in 30 ml methanol in an argon
atmosphere. Into the solution thus formed, a methanol solution in
which 10 mmol 2-mercapto-5-phenyl-1, 3, 4-oxadiazole and 5 mmol
sodium methoxide is dropped slowly.
Thereafter, the solution thus formed is stirred for three hours,
and cooled to -60.degree. C. Then, the precipitate thus created is
separated by filtration. The precipitate is decompressed and dried,
and recrystallized three times by ethanol to provide 2,
2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole).
2. Synthesis of 2, 2'-Dithiobis (5-Methyl 1, 3, 4-Thiadiazole
(Comparative Example 1)
Likewise, 2, 2'-dithiobis (5-methyl 1, 3, 4-thiadiazole) is
synthesized using 2-mercapto-5-methyl-1, 3, 4-thiadiazole in place
of 2-mercapto-5-phenyl-1,3, 4-oxadiazole.
Incidentally, in the filtration step in both cases, an object
material as well as filtered medium is contained in the filtrate.
Therefore, the object material is recovered and refined in a
separate step. The details thereof are not described here.
The product thus created has been recognized to be the object
material by a FAB mass analyzer and an infrared spectroscopic
analyzer.
Using 2, 2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole) and 2,
2'-dithiobis (5-methyl-1, 3, 4-thiadiazole), a battery was made. It
should be noted that the above steps are performed in an argon
atmosphere contained in a globe box.
As an electrolyte, two electrolytic solutions were prepared in
which lithium trifluoromethanesulfonate (LiCF.sub.3 SO.sub.3) is
solved in 30 ml .gamma.-butyrolactone of to provide a concentration
of 0.2 mmol/l. The two synthesized disulfide compounds of 2,
2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole and 2, 2'-dithiobis
(5-methyl-1, 3, 4-thiadiazole) were solved in the prepared
solutions, respectively to provide a concentration of 5 mmol/l.
Using these two solutions, with a sample electrode of glassy
carbon, a counter electrode of a platinum wire and a reference
electrode of silver/silver-ion (Ag/Ag.sup.+ (LiClO.sub.4)
electrode), the battery was made. In this case, the battery having
2, 2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole) was taken as Battery
1 (Embodiment 1) and the battery having 2, 2'-methyl dithiobis
(5-methyl-1, 3, 4-thiadiazole) was taken as Battery 2 (Comparative
Example 1). The cyclic voltamograms of Batteries 1 and 2 were
measured at 23.degree. C.
The measurement result of Battery 1 is shown in FIG. 1, whereas
that of Battery 2 is shown in FIG. 2 (In these figures, the
ordinate represents a current value in the same scale). As seen
from FIGS. 1 and 2, the peak separation between the anode peak
potential and the cathode peak peak potential is larger in Battery
2 than in Battery 1. This reveals that the Battery 1 having 2,
2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole) can take out a larger
current.
EMBODIMENTS 2-7
The test results of coin-type secondary batteries are as follows.
In these tests, in the steps where mixing of nitrogen, oxygen and
water should be obviated, work was carried out within an argon gas
flow as necessity requires. Dehydrated and distilled solvents were
used where necessity requires.
A Synthesis of active materials:
[EMBODIMENT 2]
Synthesis of 2, 2'-Dithiobis (5-Methyl-1, 3, 4-Oxadiazole)
Within a nas flask having a capacity of 300 ml, 5 mmol iodine is
dissolved in 30 ml methanol in an argon atmosphere. Into the
solution thus 10 mmol, 2-mercapto-5-methyl-1, 3, 4-oxadiazole of
and 5 mmol sodium methoxide dissolved in 30 ml methanol is dropped
slowly. Thereafter, the solution thus formed is stirred for thirty
minutes, and cooled to -40.degree. C. Then, the precipitate thus
created is separated by vacuum/filteration, thus providing 2,
2'-dithiobis (5-methyl-1, 3, 4-oxadiazole) represented by Chemical
Formula (4) (hereinafter referred to as "active material
.alpha.").
Chemical Formula (4): ##STR4##
[EMBODIMENT 3]
Synthesis of 2, 2'-Trithiobis (5-Methyl-1, 3, 4-Oxadiazole)
Within a nas flask having a capacity of 1000 ml, 1000 mmol
2-mercapto-5-methyl-1, 3, 4-oxadiazole is dissolved in 800 ml
formamide. In the solution thus formed, a 100 ml solution of
N.sub.1 N-dimethylformamide in which sulfur dichloride of 1.25
mmol/l has been solved of is dropped slowly. Upon completion of the
dropping, the solution was stirred for one hour, thus providing a
precipitate. The solution was cooled to -40.degree. C., thus
increasing the amount of precipitate. The precipitate was washed by
diethyl diethylether and subsequently decompressed and dried, thus
providing 2, 2'-trithiobis (5-methyl-1, 3, 4-oxadiazole)
represented by chemical formula (5) (hereinafter referred to as
"active material .beta.").
Chemical Formula (5) ##STR5##
[EMBODIMENT 4]
Synthesis of 2, 2'-Tetrathiobis (5-Methyl-1, 3, 4-Oxadiazole)
Like the synthesis of 2, 2'-trithiobis (5-methyl-1, 3,
4-oxadiazole), except that a solution of 125 mmol
disulfurdichloride of dissolved in 100 ml N.sub.1 N-dimethyl
formamide solution is used in place of the solution of sulfur
dichloride/N.sub.1 N-dimethyl formamide solution. 2,
2'-tetrathiobis (5-methyl-1, 3, 4-oxadiazole) which is represented
by chemical formula (6) (hereinafter referred to as "active
material .gamma."), is provided.
Chemical Formula (6) ##STR6##
[EMBODIMENT 5]
Synthesis of 2, 2'-Dithiobis (5-Phenyl-1, 3, 4-Oxadiazole)
Within a flask having a capacity of 300 ml, 5 mmol iodine is
dissolved in 30 ml methanol in an argon atmosphere. Into the
solution thus formed, 10 mmol 2-mercapto-5-phenyl-1, 3,
4-oxadiazole of 10 mmol, and 5 mmol sodium methoxide dissolved in
30 ml methanol is dropped slowly. Thereafter, the solution thus
formed is stirred for thirty minutes, and cooled to -40.degree. C.
Then, precipitate thus created is separated by vacuum filteration,
thus providing 2, 2'-dithiobis (5-phenyl-1, 3, 4-oxadiazole)
represented by Chemical Formula (7) (hereinafter referred to as
"active material .delta.").
Chemical Formula (7) ##STR7##
[EMBODIMENT 6]
Synthesis of 2, 2'-Trithiobis (5-Phenyl-1, 3, 4-Oxadiazole)
Like the synthesis of 2, 2'-trithiobis (5-methyl-1, 3,
4-oxadiazole), except that 2-mercapto-5-phenyl-1, 3, 4-oxadiazole
was used in place of 2-mercapto-5-methyl-1, 3, 4-oxadiazole, 2,
2'-trithiobis (5-phenyl-1, 3, 4-oxadiazole), which is represented
by chemical formula (8) (hereinafter referred to as "active
material .zeta.") was obtained.
Chemical Formula (8) ##STR8##
[EMBODIMENT 7]
Synthesis of 2, 2'-tetrathiobis (5-Phenyl-1, 3, 4-Oxadiazole)
Like the synthesis of 5, 5'-tetrathiobis (5-methyl-1, 3,
4-oxadiazole, except that 2-mercapto-5-phenyl-1, 3, 4-oxadiazole
was used in place of 2-mercapto-5-methyl, 1, 3, 4-oxadiazole. 2,
2'-tetrathiobis (5-phenyl-1, 3, 4-oxadiazole), which is represented
by chemical formula (9) (hereinafter referred to as "active
material .zeta."), was obtained.
Chemical Formula (9) ##STR9##
[COMPARATIVE EXAMPLE 2]
Synthesis of 2, 2'-Dithiobis (5-Methyl-1, 3, 4-Thiadiazole
Within a flask having a capacity of 1000 ml, 150 mmol of
2-mercapto-5-methyl-1, 3, 4-thiadiazole is dissolved in 450 ml
methanol. Into the solution thus prepared, 39 ml of 34.5% hydrogen
peroxide is dropped slowly. The solution was stirred for one hour
at room temperature. Thereafter, by decompression and heating,
precipitate was created. The solution was filtered and washed. By
subsequent decompression and drying, crude crystal was obtained. By
recrystallization using ethanol, 2, 2'-dithiobis (5-methyl-1, 3,
4-thiadiazole) (hereinafter referred to as "active material
.epsilon.") was obtained.
[COMPARATIVE EXAMPLE 3]
Synthesis of 2, 2'-Trithiobis (5-Methyl-1, 3, 4-Thiadiazole
Within a flask having a capacity of 1000 ml, 100 mmol
2-mercapto-5-methyl-1, 3, 4-thiadiazole is dissolved in 200 ml
tetrahydrofuran. Into the solution thus prepared, 125 mmol sulfur
dichloride is dropped slowly, thus giving precipitate. After the
dropping, the solution was stirred at room temperature for 5-10
minutes. The precipitate was filtered and washed by
tetrahydrofuran. The precipitate was decompressed and dried, thus
providing 2, 2'-trithiobis (5-methyl-1, 3, 4-thiadiazole)
(hereinafter referred to as "active material .theta.").
[COMPARATIVE EXAMPLE 4]
Synthesis of 2, 2'-Tetrathiobis (5-Methyl-1, 3, 4-Thiadiazole)
Like the synthesis of 2, 2'-trithiobis (5-methyl-1, 3,
4-thiadiazole), except that 125 mmol disulfur dichloride was used
in place of sulfur dichloride. 2, 2'-tetrathiobis (5-methyl-1, 3,
4-thiadiazole (hereinafter referred to as "active material .iota.")
was obtained.
B. Analysis of the Active Materials
Various kinds of analysis were performed for the active materials
.alpha.-.zeta.. They include CHNS/O analysis (Perkinelemer Co. Inc.
PE 2400 series II, CHNS/O analyzer), .sup.1 H-NMR spectrum analysis
and .sup.13 C-NMR spectrum analysis.
Table 1 shows the CHNS analysis and O analysis (mass ratio of
carbon, hydrogen, nitrogen, sulfur and oxygen converted into
integer ratio using nitrogen as a standard), and the molecular
weights recognized by the FAB-MS analysis. Table 2 shows the result
of the .sup.1 H-NMR and .sup.13 C-NMR spectrum analysis. FIGS. 3
and 4 show .sup.1 H-NMR and .sup.13 C-NMR spectra, respectively of
the active .alpha.. FIGS. 5 and 6 show .sup.1 H-NMR and .sup.13
C-NMR spectra respectively of the active material .delta..
TABLE 1 ______________________________________ FAB-MS Active CHNS
Analysis Result Analysis Result Material C H N S O Molecular Weight
______________________________________ .alpha. 6.0 6.1 4.0 2.0 2.0
230 .beta. 6.0 5.9 4.0 3.0 2.0 262 .gamma. 6.0 6.0 4.0 4.0 2.0 294
.delta. 16.0 9.9 4.0 2.0 2.0 354 .theta. 16.0 9.9 4.0 3.0 2.0 386
.zeta. 16.0 10.1 4.0 4.0 2.0 418
______________________________________
TABLE 2 ______________________________________ unit: PPM .sup.1
H-NMR .sup.13 C-NMR Active Deuterium CH.sub.3 C.sub.6 H.sub.5
Deuterium CH.sub.3 C.dbd.N C.sub.6 H.sub.5 Material Solvent Peak
Peak Solvent Peak Peak Peak ______________________________________
.alpha. Chloro- 2.38 Chloro- 8.9 162.4, -- form form 175.2 .beta.
Chloro- 2.40 Chloro- 9.1 162.8, -- form form 175.7 .gamma. Chloro-
2.43 Chloro- 9.2 162.8, -- form form 175.7 .delta. Acetone --
7.49.about. Chloro- -- 160.5, 123.0, 7.59 form 167.9 127.2,
8.06.about. 129.2, 8.10 132.5 .epsilon. Acetone -- 7.49.about.
Chloro- -- 160.7, 123.0, 7.60 form 167.9 127.3, 8.07.about. 129.3,
8.11 132.6 .zeta. Acetone -- 7.51.about. Chloro- -- 160.7, 123.0,
7.61 form 168.0 127.2, 8.06.about. 129.3, 8.12 132.6
______________________________________
C Making the Cathode
Mixed are the above active materials .alpha..about..iota. of 33
weight parts, lithium trifluoromethane sulfate (LiCF.sub.3
SO.sub.3) of 18 weight parts, polyethylene oxide (molecular weight:
two million) of 42 weight parts, carbon black (Kechen Black
available from Lion Co. Ltd.) of 7 weight parts. For easy mixture,
a small amount of acetonitrile is also added. The mixture is
stirred so as to be uniform. The slurry thus obtained is developed
using a Teflon petri dish and dried day and night at 80.degree. C.
to provide a film (having an average thickness of 600 .mu.m). The
film is punched out to provide a cathode having a diameter of 15
mm.
D Fabrication of the Solid Polymer Electrolyte
Acrylonitrile-methyl. acrylate copolymer of 1.5 g and
.gamma.-butyrolactone solution of 6.0 ml of lithium
trifluoromethane sulfonate (LiCF.sub.3 SO.sub.3) having a
concentration of 1 mol/l are mixed and developed on the petri dish.
The developer is heated to 120.degree. C. and gradually cooled. The
developer is punched out to provide a film having a diameter of 16
mm. This serves as a separator in assembling a battery.
E Making the Anode
The anode is made by punching out a lithium metal foil (having a
thickness of 1.2 mm) to have a diameter of 15 mm.
F Assembling the Coin-type Cell
18 coin-shaped cells (2 for each of nine kinds of coin-shaped cells
corresponding to Embodiments 2 to 7 and Comparative Examples 2 to
4) were fabricated using the cathodes containing the above nine
kinds of active materials, solid polymer electrolytes and anodes.
The section thereof is shown in FIG. 7. In FIG. 7, reference symbol
A denotes an anode cap; B an anode; C a solid polymer electrolyte
(serving as a separator); D a cathode; E a current collector made
of stainless; F a cathode can; G a gasket for separating the inside
of the battery from the outside and preventing the anode can from
contacting the cathode can.
G Evaluation of Coin-type Cells
The coin-shaped cells having the above active materials was
evaluated as follows.
For one of the two cells having the same active material, a current
of 0.2 mA/cm.sup.2 was supplied to the cathode, whereas for the
other thereof, a current of 0.4 mA/cm.sup.2 was supplied to the
cathode.
Charging/discharging was carried out within a thermostat bath at
20.degree. C. The charging was performed until the cell voltage
becomes 4.5 V at the above current density whereas the discharging
was performed until the cell voltage becomes 2.0 V. Before
evaluation, charging/discharging is repeated twice and charging is
carried out. The evaluation was performed at the subsequent
discharging. The result at the current density of 0.2 mA/cm.sup.2
is shown in Table 3, and that of the current density of 0.4
mA/cm.sup.2 is shown in Table 4. In these tables, the capacitance
density means capacitance of a cathode by weight, and the energy
density means the value of the average voltage in discharging
multiplied by the capacitance density. The using rate means the
rate of the actual amount of electricity to that when assuming that
the entire active material within the cathode contributes to
discharging.
FIG. 8 shows a discharging curve (current density: 0.2 mA/cm.sup.2
of the cells using the active materials .alpha., .delta. and .eta.
for evaluation which correspond to Embodiment 2, Embodiment 5 and
Comparative Example 2).
TABLE 3 ______________________________________ Average Specific
Discharge Energy Active Capacity Cell-Voltage Density Utilization
Material (Ah/kg) (V) (Wh/kg) (%)
______________________________________ Embodiment 2 .alpha. 60.2
2.72 163.7 78.4 Embodiment 3 .beta. 96.3 2.66 256.2 71.4 Embodiment
4 .gamma. 115.6 2.64 305.2 64.1 Embodiment 5 .delta. 46.3 2.63
121.7 92.7 Embodiment 6 .theta. 78.6 2.70 212.2 85.8 Embodiment 7
.zeta. 98.9 2.67 264.1 78.0 Comparative .eta. 49.6 2.41 119.6 73.6
Example 2 Comparative .THETA. 75.2 2.39 182.1 63.4 Example 3
Comparative .iota. 83.1 2.33 193.6 51.1 Example 4
______________________________________
TABLE 4 ______________________________________ Average Specific
Discharge Energy Active Capacity Cell-Voltage Density Utilization
Material (Ah/kg) (V) (Wh/kg) (%)
______________________________________ Embodiment 2 .alpha. 59.8
2.68 160.3 77.8 Embodiment 3 .beta. 95.5 2.65 253.1 70.8 Embodiment
4 .gamma. 113.4 2.62 297.1 62.9 Embodiment 5 .delta. 46.4 2.66
122.9 93.0 Embodiment 6 .theta. 77.5 2.63 203.8 84.6 Embodiment 7
.zeta. 98.1 2.59 254.1 77.3 Comparative .eta. 44.1 2.39 105.3 65.4
Example 2 Comparative .crclbar. 69.9 2.34 163.8 58.2 Example 3
Comparative .iota. 76.3 2.32 176.9 46.9 Example 4
______________________________________
As seen from the comparison of the secondary batteries (coin-type
cells) according to the second to fourth embodiment with those
according the second comparative example in Tables 3 and 4, the
secondary batteries using the electrode materials adopted in the
present invention have an average discharging voltage higher by
about 300 mV than those of the secondary batteries using a
thiadiazole ring. Thus, it was confirmed that the phenomenon in the
cyclic voltammetry of the first embodiment and the first
comparative example also applies to coin-type cells (secondary
batteries). It can be seen that the secondary batteries using the
electrode materials according to the present invention, which have
higher average voltages and slightly higher capacity densities than
those of the secondary batteries using the ordinary electrode
materials having the thiadiazole ring, can provide a higher energy
density than those of the latter. It can be seen that the secondary
batteries using the active materials .delta., .theta. and .zeta.
having the phenyl group according to the fifth to seventh
embodiments have a-higher using rate than those of the secondary
batteries according to the second to fourth embodiments using the
active materials .alpha., .beta. and .gamma.. This is probably
attributable to the fact that any interaction between .pi.
electrons of a phenyl group and those of carbon which serves as an
electric collector improves the conductivity of the electrode and
so improves the using rate.
Further, even if the discharging condition is increased from 0.2
mA/cm.sup.2 to 0.4 mA/cm.sup.2, the secondary battery using the
electrode material according to the present invention provides a
small reduction in the cathode utility. Thus, it was confirmed that
the secondary battery using the electrode material according to the
present invention can deal with the discharging by a large
current.
* * * * *